Milbemycin A3 oxime is an anthelmintic, a derivative of milbemycin A3 , and a component of milbemycin oxide . It reduces the number of microfilariae of the heartworm D. immitis in the blood of naturally infested dogs by 85.2% when administered at a dose of 0.05 mg/kg. Formulations containing milbemycin A3 oxime, in combination with milbemycin A4 oxime, have been used in the treatment of parasitic infections in dogs.